|
|
|
|
| pedestal
| Initial lens position before ramp begins (um)
|
|
| slope
| slope of the focus ramp (um/mm)
|
|
| length
| length of the focus ramp (mm)
|
|
| position
| position of start of ramp (mm)
|
This command set up a 'profile offset ramp' based on the command variables. On the next plot the firmware outputs the specified focus ramp. After the plot completes (or is aborted) focus ramping is cancelled until another 'foc offset ramp' command is issued.
|
|
| The best focus for a given head on a specific media is determined with empirical data when a head is manufactured and when a media is qualified. One of several useful tests for this kind of qualification is the 'focus offset ramp'. This puts the head in a mode where the focus offset is 'ramped' in a specific way along the main scan swath. The concept is to force a linear focus offset change as each swath of a plot is imaged. By measuring the distance along the swath from the start of the offset ramp to the point of ideal focus is possible to determine the offset in effect at that point and consequently the optimum focus offset value for the head. The effect of each command variable is shown below:
|
|
| |<-----length---->|
| (mm) |
| ________
| /
| /
| /
| /
| / |
| / | <--- slope
| / ----' (um/mm)
pedestal (um) | /
_________________________________/
| |
|<------- position from ------->|
begining of plate (mm) |